Pilot using too much electric charge?

[bill_rowe]

Has anyone else had a problem with electric charge usage rates when in "prograde" or "retrograde" mode? I had Jeb piloting and I had just gotten him up to the level where he can hold "prograde". I had SAS on and he was holding in stable mode just fine. Then I switched to prograde mode and he change the ship orientation correctly (it was a minor adjustment), but while holding prograde, he was using electric charge up very quickly (approx. 3-5 units per second). The ship was in ~80km Kerbin orbit, so atmosphere was not a factor. When I switched back to "stable" mode, electric power consumption returned to "normal" (a few hundredths of a unit per second). Is this rate of electric usage a bug or by design?

Thanks,

Bill Rowe

Edited January 3, 2015 by bill_rowe

[Anquietas314]

It's a bug; I've encountered that a couple times, but never quite to that extreme. It might be helpful if you post the craft file or your save (or both) of the ship in question. Most designs seem to be okay most of the time though, at least for me.

[DeMatt]

"Prograde", while in orbit, is a constantly changing vector. Jeb was therefore continually correcting the ship's heading.

Although if you're actually burning 3-5 electric charge per second, I suspect you've piled too many reaction wheels onto your ship.

[Anquietas314]

"Prograde", while in orbit, is a constantly changing vector. Jeb was therefore continually correcting the ship's heading.

The thing is, it should require barely any input from Jeb to make that correction, or none at all if you're smart about it. That translates to very little power usage, unless of course you're following prograde in low orbit of a black hole or neutron star or something. MechJeb's implementation (Smart A.S.S.) uses far less EC than stock's.

[Mesons]

This is a "Known Issue." Hopefully a fix will be released for this bug in the next update.

See http://forum.kerbalspaceprogram.com/threads/92235-Cross-Platform-Issues-Thread

[Kryxal]

I wonder if this might be related to how "jittery" the controls become in these modes ... maybe they try too hard to maintain headings and that needs to be loosened up somewhat, or damped down.

[Anquietas314]

I wonder if this might be related to how "jittery" the controls become in these modes ... maybe they try too hard to maintain headings and that needs to be loosened up somewhat, or damped down.

Yeah, that's exactly the issue. If you're a long way from the marker it's trying to follow, it'll almost always massively overdo the rotation. The solution to that is just to make it take account of how fast you're already rotating as well as how far away from the correct orientation you are. The game only seems to do the second one of those.

[wibou]

I don't know if that's your problem, but I always find that the "pilot hold" functions are WAY too aggressive.

Instead of using small torque correction and wait until the node aligns, it tends to apply the maximum torque it can give all the way there. It almost always ends up overshooting and try to correct applying again way too much torque... in the end, the pilot hold oscillates around the node for a long time.

I guess it might be what you experiment; instead of applying tiny torque to keep the node aligned, Jeb is probably applying HUGE one, then immediattely compensate with another huge push, and on and on... The result is a stable hold (torque pushes are made very close altogether), but cost way more energy than it should.

That said, the issue is especially apparent for very heavy spacecraft, as it needs huge torque to move them around, but also huge torque to STOP moving around. That's something the hold functions are just totally unable to take into account. For heavy ship, you better do use SAS just for stability and to hold the prograde/rettrograde node yourself (sorry Jeb!).

The same issue apply on very long and thin ship. Those tend to giggle a little due to the distance between the command pod and the center of mass. In that case the hold functions try to keep stable a ship that (thanks to the physic engine) just won't, wasting huge amount of energy in the process.

In fact, by trying to compensate a little giggling, it mays very well start building up gigangtic "wobble waves" that eventually tear appart the ship... For that reason, it's best to keep any SAS turned off on those long and thin ship and to operate manually.